A major safety concern for process control valves is the loss of metal and wall thickness in the body of the valve. The high fluid velocities encountered by control valves can contribute to and accelerate wear caused by the process fluid. As a result, corrosion due to loss of protective coatings and metal loss due to cavitation are accelerated. Predicting the remaining life of a valve body or the need for maintenance by regularly testing the valve body for loss of metal and decrease in wall thickness is particularly troublesome as compared to pipes because the irregular shape of the valve body does not allow for use of conventional testing techniques such as ultrasonic testing.
Where the pressure differential is large, the high velocity created within the device can be detrimental. For example, in liquid systems the resulting high velocities can produce cavitation. This occurs when the pressure at the Vena Contracta falls below the vapor pressure of the liquid, producing vapor bubbles which subsequently collapse when the bubbles enter the relatively higher pressure region downstream. The collapse of these bubbles within the device may cause physical damage to the parts through erosion, which may shorten the useful life of the device.